It's time to share some of my experiences, crazy ideas, tips and tricks !!!

Monday, March 20, 2017

vSAN stretched cluster topology explained

VMware vSAN 6.2 Stretched Cluster & 2 Node Guide covers greatly all
the network topologies supported and the configuration steps involved on
setting up such solution, but the guide does not detail some network aspects which could pass unnoticed
and cause some issues down the road in case you did not consider them during design phase.

That’s what I’m trying to help clarify today.

My example is based on VMware’s recommended architecture, a stretched L2 network between data sites and L3 network between data sites and
witness site.

If you follow the guide, soon you will notice
the hosts from both sites would use the same gateway.

If you implement something like that, the traffic
from Site B would have to transverse the link between sites in order to reach
the witness site.

Guest what, in case of link failure between witness site and Site A, link failure
between sites or gateway (192.168.0.1) failure, hosts on site B would also be unable
to reach the witness, even though there’s an alternate path through the gateway on
site B (192.168.0.129).

Without access to the witness, the hosts on site B, would not have access
to 50% plus of the components and then would not be able to run or restart any
VM on it.

Back to my hypothetical scenario, to avoid this cross-link situation and
make the hosts use their own local gateway and links this is what I’m
proposing.

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Who am I

I’m an IT specialist with over 15 years of experience, working from IT infrastructure to management products, troubleshooting and project management skills from medium to large environments.
Nowadays I'm working for VMware as a Consulting Architect, helping customers to embrace the Cloud Era and make them successfully on their journey.
Despite the fact I'm a VMware employee these postings reflect my own opinion and do not represents VMware's position, strategies or opinions.
Reach me at @dumeirell